Percutaneous oxygenator with transverse hollow fibers

Abstract: An intravenous fiber membrane oxygenator is disclosed in several embodiments wherein the fibers either run at a transverse angle relative to the longitudinal axis of the oxygenator and/or are of a reduced length to optimize the gas transfer efficiency of the oxygenator. Various helical or spiral wraps of fibers are disclosed. One embodiment utilizes two sets of longitudinally extending fibers wherein the oxygen gas is moved in opposite directions from a central location of the oxygenator.

Description: The present invention concerns an elongated percutaneous oxygenator according to the precharacterizing portion of claim 1 The present invention relates generally to gas transfer devices and more particularly to a percutaneous intravenous oxygenator utilizing hollow gas permeable fibers. Many types of blood oxygenators are well-known in the art. For example, during open heart surgery, the patient is interconnected with an external oxygenator, commonly known as a heart-lung machine, which introduces oxygen into the blood system. Most types of oxygenators use a gas permeable liquid impermeable membrane. Blood flows along one side of the membrane, and oxygen is supplied to the other side of the membrane. Given a sufficient pressure gradient between the oxygen supply and the blood, the oxygen will diffuse through the membrane and into the blood. In addition, carbon dioxide will tend to diffuse from the blood through the membrane. In other situations, a smaller, implantable oxygenator may be sufficient to adequately supplement the patient's cardiopulmonary function by marginally increasing the oxygen content of the patient's blood. For example, patients suffering from emphysema, pneumonia, congested heart failure, or other chronic lung disease often have blood oxygen partial pressures of approximately 5320Pa(40 torr). A relatively small increase of 10% to 20% is generally sufficient to adequately maintain the patient. This is a particularly desirable alternative in that it avoids the need to intubate the patient in such cases. In addition, temporary use of this type of oxygenator is sufficient in many cases to tie the patient over in acute respiratory insult. Placing such patients on a conventional respirator is often the beginning of a progressive down hill spiral by damaging the patient's pulmonary tree and thereby causing greater dependence on the respirator. The effective rate of diffusion in percutaneous oxygenators can be limited in some instances by the problem of "streaming" or "channeling," in which the blood stream establishes relatively stable patterns of flow around and through the oxygenator. Portions of the oxygenator are exposed to a relatively high velocity, turbulent flow of blood. These conditions tend to increase cross-diffusion of oxygen and carbon dioxide. However, other portions of the oxygenator are exposed to a low velocity, laminar flow of blood which reduces diffusion of gases. Those portions of the oxygenator immediately adjacent to the regions of the high blood flow may continue to experience high rates of diffusion, but the remaining portions of the oxygenator tend to have relatively low diffusion rates. Thus, the overall diffusion rate of the oxygenator can be substantially diminished by streaming. A number of devices and processes have been invented in the past relating to different types of oxygenators. US-A-3,505,686 to Bodell demonstrates the general concept of using gas permeable fibers to boost the oxygen level of blood. The patent discloses several variations of the device wherein it is intended for use inside the body of the patient. In the implantable embodiment of the Bodell device, a tubular casing serves as a shunt either from the pulmonary artery to the left atrium of the heart or more generally between an artery and a vein. A multitude of parallel-connected capillary tubes are used to oxygenate and/or purify the blood circulating to the casing. US-A-4,583,969 to Mortenson shows a transvenous oxygenator made of a plurality of small diameter gas permeable tubes connected to headers at each end. However, the specific device disclosed by Mortenson has a significant disadvantage in that two incisions are required. US-A-4,631,053 to Taheri discloses a transvenous oxygenator having a single membrane through which oxygen diffuses. The membrane is disposed within a sheath and both are supported by a flexible wire. US-A-4,850,958 to Berry, et al. discloses an in vivo extrapulmonary blood gas exchange device having a bundle of elongated gas permeable tubes bound at each end and enclosed within respective air tight proximal and distal chambers. A dual lumen tube is situated relative to the gas permeable tubes such that an outer lumen terminates within the proximal chamber and inner lumen terminates within the distal chamber. US-A-4,911,689 to Hattler and US-A-4,986,809 to Hattler, et al. disclose several embodiments of percutaneous oxygenators. In the simplest embodiment, oxygen is circulated through a plurality of hollow, gas permeable fibers forming loops and the device is inserted through a single incision into a blood vessel. In other embodiments, the fiber loops are bisected and placed in fluid communication within a mixing chamber within a tip at the distal end of the device. The DE-U-9002100, which is used as a basis for the preamble of claim 1, describes an apparatus for the oxygenation of blood and for the elimination of CO 2 in blood comprising a capillary membrane bundle closed at one end by a gas intake cap and at the other end by a gas outlet cap whereby the gas inlet cap is connected to a gas intake tube and the gas outlet cap is connected to a gas outlet tube. Due to the inherent desirability and need for devices of the above described type, continuing efforts are being made to improve the efficiency of the gas transferred provided by the device and it is to meet these needs that the present invention has been developed. The elongated percutaneous oxygenator of the present invention is defined in the characterizing portion of claim 1. The present invention was developed to improve upon prior art oxygenators of the type that include hollow gas permeable/liquid impermeable membrane fibers that can be inserted into the vena cava to oxygenate blood intravenously. It has been found that the efficiency of such oxygenators can be improved by minimizing the length of the fibers and deploying the fibers so that they do not run longitudinally of the device as in prior art systems. The blood gas transfer can also be improved by maintaining constant movement of the gas fibers through use of an inflatable balloon around which the fibers extend. Several embodiments of an oxygenator in accordance with the above teachings are disclosed. In a first embodiment of the invention, an elongated tubular gas delivery manifold is connected to one end of a plurality of gas fibers with the manifold extending longitudinally of the oxygenator. A similar elongated tubular gas exhaust manifold is connected to the opposite end of the fibers and the fibers are wrapped around one of the manifolds as well as an inflatable and deflatable balloon so that several layers of the fibers can be wound transversely around the balloon. Circumferential displacement of the manifolds in one direction or another serve to increase or decrease the diameter of the oxygenator so that it can be decreased in diameter for easy insertion into the vena cava of a patient and increased in diameter while in the vena cava for optimal gas transfer. In a second embodiment, two sets of gas permeable fibers are interwoven with the fibers of each set extending in parallel relationship with each other and substantially perpendicular to the fibers of the other set. One set of fibers extends longitudinally of the device and the other set transversely. An elongated semi-rigid manifold is connected in fluid communication to the input end of one set of fibers as well as to a substantially perpendicular but flexible elongated tubular manifold which is connected in communication to the input end of the fibers of the second set. A duplicate set of manifolds are connected to the outlet ends of the fibers so that the fibers and the flexible manifolds can be wound around one of the semirigid elongated manifolds and a balloon so as to be configured similarly to the second described embodiment. As will be appreciated, however, with this arrangement, twice the number of fibers can be utilized thereby increasing the gas transfer efficiency of the device. In a third embodiment of the invention, elongated tubular inlet and outlet manifolds extend longitudinally of the device and are connected to inlet and outlet ends of gas permeable fibers which extend transversely to the manifolds and form a tubular construction of fibers around an interior inflatable balloon. Gas is delivered to the inlet manifold and allowed to flow in opposite directions through the fibers and around the tubular body for collection at the outlet manifold which is connected to a vacuum source so that the gas flow can be maintained at a negative pressure. Several layers of fibers comprising the tubular body can be provided in alternative arrangements of this embodiment. Other aspects, features and details of the present invention can be more completely understood by reference to the following detailed description of the preferred embodiments, taken in conjunction with the drawings, and from the appended claims. Fig. 1 is an isometric view of a first embodiment of the present invention with an alternative arrangement shown in phantom lines. Fig. 2 is an isometric view of the oxygenator shown in Fig. 1 in a reduced diameter configuration. Fig. 3 is a section taken along line 12-12 of Fig. 1. Fig. 4 is a section taken along line 13-13 of Fig. 2. Fig. 5 is an enlarged fragmentary section taken through the inlet manifold of the oxygenator of Fig. 1 showing the connection of the manifold to the fibers. Fig. 6 is an isometric view of the oxygenator of Fig. 1 in an unrolled state and with the balloon shown in phantom lines in the alternative arrangement. Fig. 7 is an isometric view of a balloon used in a second embodiment of the present invention. Fig. 8 is an enlarged section taken along line 17-17 of Fig. 7. Fig. 9 is an enlarged section taken along line 18-18 of Fig. 7. Fig. 10 is an isometric view of the second embodiment of the present invention in an unrolled state and without the internal balloon. Fig. 11 is an enlarged section taken through portions of the inlet and outlet manifolds of the oxygenator of Fig. 10 showing their relationship with two interwoven sets of fibers. Fig. 12 is an isometric view of a third embodiment of the present invention. Fig. 13 is an enlarged section taken along line 28-28 of Fig. 12. Fig. 14 is an isometric view with parts removed of a modification to the embodiment shown in Fig. 12 . Fig. 15 is a section taken along line 30-30 of Fig. 14. Membrane type oxygenators are characterized in general by the fact that oxygen rich gas will diffuse through the membrane into oxygen deficient blood on the opposite side of the membrane while excess carbon dioxide in the blood will cross-diffuse through the same membrane into the oxygen stream. Accordingly, when a membrane oxygenator is inserted in a blood vessel and oxygen passed therethrough, the oxygen will diffuse through the wall of the fiber membrane thereby oxygenating the blood and simultaneously removing excess carbon dioxide from the blood. It should be appreciated that the oxygenator of the present invention could be used in other gas transfer environments such as for example to deliver an anesthetic. A better description of this particular alternate use can be found in US-A-5,207,640. A first embodiment 80 of the present invention is shown in Figs. 1 - 6 and can be seen to include a fiber mat 82 formed of a plurality of parallel bound fibers 84 and elongated longitudinally extending tubular inlet and outlet manifolds 86 and 88, respectively, connected to opposite ends of the mat for delivering gas to the fibers and removing gas from the fibers. The entire mat 82 can be wound in a spiral around one of the manifolds and an interior balloon 90 which is inflatable and deflatable as with the first embodiment. The fibers 84 in the fiber mat 82 extend substantially perpendicularly to the longitudinal axis of the oxygenator and are bound together as in the first described embodiment with threads 92 or the like so that the fibers are retained in substantially parallel but spaced relationship for optimal gas transfer. The inlet manifold 86 is connected to input ends 94 of each fiber 84 and the output manifold 88 is connected to the output ends 96 of each fiber as best seen in Fig. 5. The manifolds are semi-rigid tubes which retain the mat in a substantially extended condition while being flexible enough to be inserted into a vein and follow the contours of the vein. The manifolds 86 and 88 are hollow tubular bodies and the fibers are potted in a suitable potting compound 98 in an opening 100 in the side of the manifolds (Fig. 5) . It does not matter whether the inlet manifold 86 is disposed adjacent to the balloon 90 so that the fiber mat is wrapped therearound or whether the outlet manifold 88 is so positioned. For purposes of the present disclosure, however, the inlet manifold 86 is disposed on the outside of the oxygenator 80 and is connected via flexible tubing 102 to a source of oxygen (not shown). The outlet manifold 88 is similarly connected with flexible tubing 104 to a vacuum source (not shown) so that the vacuum source can draw the oxygen and any accumulated carbon dioxide through the manifolds and the connected fibers at a negative pressure. The balloon 90 which is disposed interiorly of the wrapped fiber mat 82 is inflated and deflated in a conventional manner through a flexible tube 106 which is connected to a source of helium or the like which has been found to be suitable for this purpose. In an alternative arrangement of this embodiment, the balloon 90 might be connected to one of the manifolds 86 or 88 with a connector 108 which in the disclosed alternative shown in phantom lines in Figs. 1, 2 and 6 is the outlet manifold 88. The connection of the balloon to one of the manifolds facilitates simultaneous insertion of the manifolds, mat and balloon. The connection does not necessarily have to be made, however, as the balloon can be inserted into the vena cava after the fiber mat is inserted and merely slid into the space 110 defined at the center of the spirally wound fiber mat. A second embodiment of the invention is illustrated in Fig. 7-11 with this embodiment being somewhat similar to that disclosed in Figs. 1-6. In the second embodiment, however, the fibers 112 are woven into a mat 113 so that there are two sets of parallel fibers 112A and 112B with the fibers in each set being substantially perpendicular to the fibers of the other set. Each set of fibers has an inlet end 114A or 114B and an opposite outlet end 116A or 116B. Manifolds 118 are generally L-shaped having a semi-rigid tubular manifold leg 120 and a perpendicular flexible tubular manifold leg 122. The rigid legs 120 are associated with one set of fibers 112A with one rigid leg communicating with the inlet ends 114A of the fibers and the other rigid leg with the outlet ends 116A of the fibers. Similarly, the flexible legs 122 are associated with the second set of fibers 112B with one flexible leg being in communication with the inlet ends 114B of the second set of fibers and the other flexible leg with the outlet ends 116B of the second set of fibers. The fibers 112 are suitably connected to the manifolds 118 with a potting compound 124 as shown in Fig. 11. One L-shaped manifold is of course connected to a source of oxygen (not shown) through an input line 126 while the other L-shaped manifold is connected to a vacuum source (not shown) through an outlet line 128. The woven fiber mat 113 is wound around a balloon 130 configured as shown in Fig. 7 with the semi-rigid manifold leg 120 of each manifold 118 extending longitudinally of the oxygenator and in parallel relationship with the balloon. The flexible legs 122 of the manifolds are allowed to be wound into a spiral at proximal and distal ends of the oxygenator respectively. The woven mat 113 of fibers is therefore wound in a spiral around the balloon and the diameter of the oxygenator can be varied by moving the semi-rigid manifolds 120 circumferentially relative to each other in one direction or another to facilitate insertion and desired operation of the oxygenator. Of course, the ability of the semi-rigid manifolds to move circumferentially relative to each other allows the fiber mat 113 to expand and contract when the balloon is inflated and deflated respectively. One desired aspect of this embodiment of the invention is the fact that nearly twice the number of fibers can be incorporated into the same mat to increase the surface area of contact between the fibers and the blood to be oxygenated. A third embodiment of the present invention is illustrated in Figs. 12-15 with a first arrangement 160 shown in Figs. 12 and 13. In this arrangement, longitudinally extending inlet and outlet manifolds 162 and 164, respectively, are of elongated semi-rigid tubular construction and are diametrically disposed on either side of the oxygenator. Of course the inlet manifold 162 is connected through an inlet tube 166 to a source of oxygen gas (not shown) while the outlet manifold 164 is connected through an outlet tube 168 to a vacuum source (not shown). The fibers 170 are disposed in two sets 170A and 170B with each set being of generally semi-cylindrical configuration and having a plurality of parallel fibers that have been bound together with thread 172 or the like so as to retain the fibers in a spaced relationship and wherein they extend substantially perpendicularly to each of the manifolds. The fibers of each set extend away from each manifold in an opposite direction so as to define a tubular body 174 that surrounds an inflatable balloon 176. The balloon as in other embodiments is connected to a source of gas (not shown) through a gas supply tube 178 for inflation and deflation with a suitable gas being helium. One advantage with an embodiment of this type is that the length of each fiber 170 is relatively short which has been found to increase oxygen transfer efficiency of the oxygenator as a whole. In a second arrangement 180 shown in Figs. 14 and 15, elongated tubular semi-rigid input and output manifolds 182 and 184, respectively, are again connected to sources of oxygen gas through an input line 186 and a vacuum source through an outlet line 188, respectively. In this arrangement, however, there are actually four sets of fibers 190 which have been bound together into four mats 190A, 190B, 190C and 190D having inlet and outlet ends 192 and 194, respectively, of the fibers in each mat connected in fluid communication with the inlet and outlet manifolds 182 and 184, respectively. The four sets of fibers define in combination two concentric tubular bodies 196 and 198 which surround an internal balloon 200 which again is connected to a gas inflation and deflation source such as helium through a gas supply tube 202. The only difference in this arrangement and that shown in Figs. 12 and 13 is that there is a double layer of thickness of the fibers to increase the surface area of contact between the fibers and the blood flow. It will be appreciated from the above description of the present invention that different embodiments of the oxygenator of the present invention have been illustrated which improve the gas transfer capabilities of intravenous fiber membrane oxygenators. Part of the improvement is felt to be due to the fact that the fibers extend at a transverse angle to the longitudinal axis of the oxygenator and also due to the fact that in several embodiments, the fibers have been shortened while retaining a desired surface area contact with the blood. Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made by way of example, and changes in detail of structure may be made without departing from the scope of the invention, as defined in the appended claims.

Claims: An elongated percutaneous oxygenator (80; 160; 180) having a longitudinal axis comprising in combination: a plurality of hollow gas permeable and liquid impermeable fibers (84; 112; 170; 190), said fibers (84, 112; 170; 190) having an input end (94; 114A, 114B) and an output end (96; 116), a first lumen (102; 128; 166; 186) connected in fluid communication with the input end (94; 114A, 114B) of said fibers (84; 112; 170; 190), a second lumen (104; 126; 168; 188) connected in fluid communication with the output end (96; 116) of said fibers (84; 112; 170; 190), gas moving means for delivering oxygen to said first lumen (102; 128; 166; 186) and removing gas from said second lumen (104; 126; 168; 188), at least some of said fibers (84; 112A; 170; 190) extending to some degree transversely to said longitudinal axis, characterized in that said first (102; 128; 166; 186) and second (104; 126; 168; 188) lumens include elongated semi-rigid tubular manifolds (86, 88; 118; 162, 164; 182, 184) extending in parallel relationship with the longitudinal axis of the oxygenator (80; 160; 180), and said fibers (84; 112A; 170; 190) extend substantially perpendicularly to said manifolds (86; 88; 118; 162; 164; 182; 184) and wherein said fibers (84, 112A; 170; 190) are wound around one of said manifolds 86, 88; 118; 162, 164; 182, 184). The elongated intravenous percutaneous oxygenator (80; 160; 180) of Claim 1 characterized in comprising a balloon (90; 130; 176; 200) extending along the length of the oxygenator, and gas inflation means in communication with a third lumen (106; 178; 202) for inflating and deflating said balloon (90; 130; 176; 200), and said plurality of hollow gas permeable and liquid impermeable fibers (84; 112; 170; 190) surrounding said balloon (90; 130, 176; 200). The oxygenator (80; 160; 180) of Claim 2 characterized in that said fibers (84; 112; 170; 190) are spirally wound from their input end to their output end about the longitudinal axis of the oxygenator. The oxygenator (80; 160; 180) of Claim 3 characterized in that there are several sets (112A; 112B; 170A, 170B;190A, 190B; 190C, 190D) of said fibers with each set including a plurality of substantially parallel fibers and wherein the sets are at least partially overlapped and spirally wound in more than one direction. The oxygenator (80; 160; 180) of Claim 4 characterized in that the fibers (84, 112; 170; 190) in each set are bound together in substantially spaced relationship to define mats of said fibers. The oxygenator (80) of Claim 2 characterized in that there is a communication between said balloon (90) and said first and second manifolds (86,88) with a connector The oxygenator (80; 160; 180) of Claim 4 characterized in that said first and second manifolds (86, 88; 118; 162, 164; 182, 184) are relatively movable along said longitudinal axis. The oxygenator (80; 160; 180) of Claim 4 characterized in that said fibers (84; 112; 170; 190) are bound together in substantially parallel spaced relationship to form a mat of said fibers. The oxygenator of Claims 1 or 2 characterized in that there are first (112A) and second (112B) sets of said fibers (112), the fibers in each set extending substantially parallel to each other and substantially perpendicularly to the fibers in the other set, each of said manifolds (118) including a semi-rigid tubular manifold leg (120) and a flexible elongated tubular manifold leg (122), said manifolds (118) of the first lumen (128) being substantially mutually perpendicular and the manifolds (118) of the second lumen (126) being substantially mutually perpendicular, and wherein said fibers (112A) are wound around one of said semi-rigid manifold legs (120). The oxygenator of Claims 1 or 2 characterized in that said fibers (170A, 170B) are bound together in spaced relationship to form a tubular mat of said fibers (170A, 107B), said fibers being oriented to form a hollow tube extending along said longitudinal axis. The oxygenator of Claim 10 characterized in that there are a plurality of tubular mats (190A; 190B; 190C; 190D) of said fibers.

Inventors: BOROVETZ HARVEY S, HATTLER BRACK G, REEDER GARY D, SAWZIK PATRICIA J, WALTERS FRANK R, BOROVETZ, HARVEY S., HATTLER, BRACK G., REEDER, GARY D., SAWZIK, PATRICIA J., WALTERS, FRANK R.
Applicants: ELECTROMEDICS INC, HATTLER BRACK G, ELECTROMEDICS, INC., HATTLER, BRACK G.
Application year: 1994
Main classification: A61M1
IPC codes: A61M1